Propeller



5 T WARD May 1939.

PHOPELLER Filed Sept. 22, 1957 2 heets-Sheet 1 E. T. WARD PROPELLER May30, 1939.

2 Sheets-Sheet 2 Filed Sept. 22, 1957 I U u 1 U, M w,

Patented May 30, 1939 UNITED STATES PATENT" OFFICE 4 Claims.

This invention pertains to propeller blades for ventilating fans andother purposes and, more particularly, to the construction of blades ofthe air-foil section type. While the ,invention will be 5 disclosedherein as embodied in a three bladed propeller for fans of the aircirculating type, it should be understood as susceptible of embodimentin propellers having any number of blades for use in fans or for otherpurposes. I

Propellers of the air circulating type are usually of relatively largesize, that is, have long blades, and are designed to operate at fairlyhigh speed so as to create a considerable volume flow of air over theheads of persons whose coml5 fort is to be increased, thereby to inducesecondary air flow toward and along the air column and thereby, in turn,to create a constant circulation of a large body of air. Such fans areparticularly useful in the home and oflice and in places subjected tohigh temperatures and high relative humidity such as factories,laundries, theatres and the like. 7

However, one of the chief objections and difii- -culties encounteredwith fan propellers of this type is the disturbing noise created by theblades when the propeller is in operation. This difflculty has been wellrecognized and while many attempts have been made to eliminate it, few,heretofore, have been successful to any substantial degree.Nevertreless, I have found that my specially designed blade so farreduces the noise as closely to approach absolute quietness, theremaining noise, if any being no more than a very minor low'pitched humwhich is barely noticeable even to the trained ear.

Consequently one of the primary objects of the invention is to provide apropeller blade so constructed and arranged that it will serve tocirculate a considerable volume of air per unit of time withsubstantially total elimination of all objectionable noises so commonlyand usually encountered with propellers of the character mentioned.

Considerable difliculty has been encountered in manufacturing theseveral blades of' an air circulator propeller so that such blades aresubstantially identical in weight, weight distribution, blade spacing,pitch, thrust, and the like. These difliculties are particularlyapparent when the propeller blades and the hub are formed as a singleunitary structure as by casting. Casting or other forming processes,even though utmost care is used in the process, including the formationof the master pattern, preparation of the match plate and meticulouscare in preparation of the mold, leave much to be desired andconsiderable time and effort in machining, balancing and matching mustbe expended upon the cast or otherwise formed unit before the severalblades may be said to be equalized or matched 5 and in dynamic andstatic balance.

I have found that many of the above mentioned manufacturing difficultiesmay be eliminated, or reduced if not eliminated, and that manufacturingefliciency may be substantially 10 increased by castingeach blade of aparticular propeller in the same casting mold which must be of a more orless permanent nature, or by molding the blades individually from aplastic composition such as a phenolic condensation 15 product, or oneincluding substantial proportions of rubber, and in the same or inseparate 'more or less permanent molds and thereafter assembling theblades on a pre-formed hub structure which may be made of metal or of 20molded composition. Under such mode of cons'tructlon all blades formedin the same mold will be found to be identical or substantially so inweight and balance as well as in conformation, size, etc., in which casethose blades molded 25 in the same mold may be arranged in matched setsfor use in the manufacture of particular propellers. Then too, bymolding or casting the blades individually, it is possible to conserveand to utilize considerable molding press or casting space which wouldbe lost or unavailable were all of the blades and the single hub of apropeller to be molded integrally, for it is thus possible to provide aplurality of molding cavities in a single molding block or castingapparatus. 35

Therefore another important object of the in-- vention is to provide ablade and hub construction of such character that the propeller bladesmay be molded or otherwise'formed individually from metal or fromcomposition materials and o thereafter secured in dynamic and staticbalance to a hub of metal or composition material, with a minimum oflabor and expense.

A further object is to provide a novel and peculiarly efiicient methodof manufacturing pro- 45 pellers of the character described.

Various other objects as well as the many advantages and uses of theinvention will become apparent and understood upon reading the followingdescription of a preferred embodiment nated section' lines, in section,the camber and. pitch of the lift or suction and thrust sides of theblade," at those sections.

Fig. 2 is a'vertical edge elevation taken along "length of the line 33.The fragment is twice the size of the blade in Fig. 1.

Fig. 4 is a vertical edge elevation viewing the blade from the sideopposite that shown in Fig. 2 and showing the leading edge of the blade,the blade of this view having a modified hub construction although beingotherwise substantially identical with the blade illustrated in Figs. 1to 3 inclusive.

Fig. 5 is a plan view of one side or end of the hub of a multi-bladedpropeller composed of individually and separately formed blades, such asthe blade illustrated in Fig. 4, and illustrating one method by whichthe blades may be assembled and held in assembled relation with oneanother.

Fig. 6 is a section taken substantially along the section line 6-6 ofFig. 5.

Fig. 7 diagrammatically illustrates a two part mold for molding orcasting a plurality of similar propeller blades at one and the sametime, the blade forms being arranged in nested relation to one another,and

Fig. 8 is a diagrammatic view of a two part mold for molding or castingsimilar propeller blades but differing from the two part mold of Fig. 7in that the blade cavities are arranged radially or fan-wise.

The blades illustrated in Figs. 1 to 4 inclusive, except for the factthat the blades of Figs. 1 to 3 are illustrated as integral with oneanother at the hub while the blade of Fig. 4 is illustrated as anindividual blade separate from any other blades of the propeller, areidentical in contour, proportions and shape and a description of onewill apply to the others.

Viewing Fig. 1, it will be noted that the blade has an irregularapparent shape with a sweepback from approximately the mid-portion ofthe length of the leading edge 10 to the tip, the trailing edge I Ihaving a similar but non-conforming sweep-back. The blade is of air-foilsection, the camber and pitch of which along line l2 and looking in thedirection of the arrows shown thereon, is relatively high, graduallydecreasing from the hub portion through the sections taken along linesl3 and it (looking in the direction of the arrows applied to thoselines) through the tip portion. At the tip on the trailing edge, the

blade has a rearwardly (as regards the direction j plane perpendicularto the axis of rotation, and

the leading edge ill, for substantially half of its radial length, maybe said to lie substantially in another and parallel plane perpendicularto the axis of rotation as is most clearly illustrated in Fig. 4. Thetrailing edge It is carried relatively abruptly rearwardly at its tipportion l5 as described above, with such 'tip portion also beingcurvedtoward the trailing edge part as-shown in Fig. 1 and toward theplane through theKprincipal portion of the leading edge Hi as shown atthe right side of the blade in Fig. 4, or'at the left side in Fig. 2.Fig. .4 also illustrates that the outer half of the leading edge III ofthe blade is gradually curved for about one-half of its length towardthe plane in which the trailing edge I6 has been described as lying andthence curves back toward and somewhat short of the plane in which themajor inner portion of the leading edge of the blade lies. The blades asthus constructed and shaped have been found to be relatively noiselessand it would seem that this result may be very largely, if not wholly,attributed to the peculiar projecting and curving tip portion, includingthe portion i5. High rotational speeds of blades shaped or constructedas above described have failed to produce more than a low pitchedunobjectionable hum. As an example of rotational speeds of commercialembodiments of the invention, representative 22-inch propellers 'rotatefrom 1140 R. P. M. to 1725 R. P. M. while representative 28-inchpropellers operate at speeds from 860 R. P. M. to 1140 R. P. M.

While the three-bladed propeller illustrated in Fig. 1 has bladesintegrally connected through a hub H which is centrally drilled as at I8for reception of a motor shaft and to which the propeller may be securedas by a set screw IS, the blades illustrated in Figs. 4 to 6 inclusive,are individually formed with mating hub sections which when assembledcomprise the entire propeller. This feature of the invention will bedescribed in connection with a three-bladed propeller, but, as willbecome apparent, two or more bladed propellers may be constructed afterthe same manner.

Each blade has a hub portion formed as a boss 2i projecting axially ateach side. provide arcuate shoulders or surfaces 22 which, when thethree blades of the type illustrated are assembled in mating relationwith one another, form a more or less continuous circular outwardlyfacing shoulder over which cup shaped hub caps 23 may be disposed intight clamping engagement therewith. The hub caps 23 in turn may be heldin place and together by a hollow bushing or ferrule 24, the ends ofwhich may be riveted over the bottoms of the caps, about centralapertures therein, as at 25 to hold the assembly together. The motorshaft is adapted to pass through the bushing 24 and may be held theretoas by a set screw 26.

Figs. 7 and 8 illustrate top and bottom portions of multi-cavity moldswhereby a plurality of individual blades may be molded or castsimultaneously. However, this is primarily for purposes of convenience.The preferred form comprises a plurality of separate molds as will beexplained. Assuming that the platform or the like on the press, orcasting apparatus for metal or composition blades is substantially thesize of the mold of Fig. 7 or of Fig. 8, separate molds for individualblades may be positionedon such platform in a parallel relation as inFig. 7 with each two corresponding cavities forming an individual orseparate mold. Or, if desired, the separate molds, each of an outsideshape approximating the segment of a circle, may be positioned fan-wiseon the apparatus. In the form illustrated in Fig. 7, one part of whichis designated 21 and the other part 28, irregularly but correspondinglylocated pins and depressions 28 These bosses and 3 I, respectively, areadapted to interfit when the mold parts are super-imposed upon oneanother, thereby to dispose the corresponding cavities A, A, B, B, etc.,in exact registration with one another. The various cavities are nestedin the respective mold parts in order to conserve space in a press orcasting machine or the like, and after the individual blades have beenformed therein, all blades formed in the mold A--A will be segregated ina lot separate from all blades formed in the mold'cavities BB', etc.,and 3-13 from all others in like manner. Thereafter the blades formed incavities AA may be utilized in the manufacture of one or moremultibladed propellers since each blade, unless defective for somereason, will be substantially identical with every other blade formed inthat particular mold cavity. The mold form illustrated in Fig. 8comprises two parts 3| and 32 adapted to register with one another inpredetermined relation when super-imposed one on the other, through pins33 and 34. In this form or mold the mold cavities are nested in fan-wiseor radial array.

While I have illustrated and described a preferred form of the inventionand certain alternatives, it should be appreciated and understood thattheinvention is of broader scope and susceptible of other embodimentswherefore I desire to be limited only by the spirit of the invention andthe scope of the appended claims.

I claim:

1. A propeller blade adapted to operate in air comprising, a one-pieceair-foil section blade having a sweep-back rearwardly, as regards thedirection of rotation, from a portion outwardly of a hub portion towardand to the tip portion, the leading and trailing edges lying betweenparallel planes perpendicular to the axis about which the blade is torotate, the trailing edge lying substantially in one of said planes fromadjacent to the hub portion to adjacent to the tip portion and thencedeparting toward the other plane,

the leading edge lying substantially in the other ing curved onrelatively short radii toward saidtrailing edge part and toward saidother plane. 2. A propeller blade adapted to operate in air comprising,a one-piece air-foil section blade having a sweep back rearwardly, asregards the direction of rotation, from a portion radially outward of ahub portion and having a pitch and camber decreasing from the hubportion toward the tip, the leading and trailing edges lying betweensubstantially parallel planes perpendicular to the axis about which theblade is to rotate, the trailing edge lying substantially in one of saidplanes from adjacent to the hub portion to adjacent to the tip portionand thence departing toward the other plane, the leading edge lyingsubstantially in the other of said planes from adjacent to the hubportion substantially to the beginning of the sweep-back and thencedeparting gradually toward the first said plane for a portion of itsremaining length and thence returning toward the other plane, thetrailing edge at the tip portion thereof being relatively abruptlycarried rearward as regards the direction of rotation, and the tipportion between the leading and trailing edges being curved from thefirst said plane toward said-other plane.

3. A propeller blade adapted to operate in air comprising, a one-pieceair-foil section blade having a sweep-back rearwardly, as regards thedirection of rotation, from a portion radially outward of a hub portionand having a pitch decreasing from the hub portion toward the tip, theleading and trailing edges lying between substantially parallel planesperpendicular to the axis about which the blade is to rotate, thetrailing edge lying substantially in one of said planes from adjacent tothe hub portion to adjacent to the tip portion and thence departingtoward the other plane, the leading edge lying substantially in theother of said planes from adjacent to the hub portion substantially tothe beginning of the sweep-back and thence departing gradually towardthe first said plane for a portion of its remaining length and thencereturning toward the other plane, the trailing edge at the tip portionthereof being relatively abruptly carried rearward as regards thedirection of rotation, and the tip portion between the leading andtrailing edges being curved from the first said plane toward said otherplane.

4. A propeller blade adapted to operate in air having an outer or thrustface and an inner or suction face, said blade including a tip portionand a hub portion, and having a leading edge and a trailing edgeintermediate said tip portion and hub portion, the camber of such bladedecreasing from the hub portion to the tip portion, said blade varyingin its width from a relatively narrow width adjacent the tip portion andadjacent the hub portion, to a greater width inter-o mediate said tworelatively narrow width portions, with said leading edge following arelatively uniform sweep-back configuration from hub portion to tipportion, and said trailing edge following an irregular line due to saidvariations in width, and with said tip portion extending relativelyabruptly rearwardly as regards the direction of rotation of said blade,and also being curved on a relatively short radius at the end of saidtip portion in an inward direction as regards the outer or thrust faceof the blade and the inner or suction face thereof.

. EDGAR T. WARD.

